The disclosure relates generally to a cold foil deposition system in which the use of cold foil is optimized. More specifically, the disclosure relates to the use of a moveable foil roller assembly, operated by a control unit that alternatively engages one or more foil rollers with an impression cylinder so as to deposit foil onto a substrate.
Various foil deposition systems are known that attempt to control the deposition of foil onto substrates as part of a printing process. U.S. Pat. No. 6,491,780, issued to Gallagher, provides one method of controlling the deposition of foil in which the speed of the foil carrier is varied during different portions of the foil transfer process. During an active transfer portion of the foil deposition process, a segment of the carrier is moved at the same speed as the substrate. In between active foil deposition segments, the foil carrier speed is sharply reduced, possibly even reversed, in order to maintain a slower average advancement speed of the foil carrier so as to match a reduced speed with which the foil is being deposited. A microprocessor-controlled shuttle mechanism, separate and distinct from any impression rollers or foil deposition rollers, is moved by a motor control system such that the foil transfer operation moves in synchrony with the speed of the substrate movement.
Other existing systems, for example U.S. Patent. Pub. Nos. US2007/0212490 and US2007/0212590, both to Preisner et al., disclose foil deposition systems in which a partial pressing surface is provided for on a press cylinder. The foil that is then fed between the press roller and an impression cylinder is only deposited on the substrate at the locations corresponding to the contacting portions of the partial pressing surface and the impression cylinder. As in Gallagher, Preisner et al. also discloses varying the advancement speed of the foil carrier by influencing the action of the foil advancement and collection rolls, including substantially stopping the foil advancement when no foil transfer is taking place. As a further refinement to the foil transfer process, Preisner et al. also discloses that the foil may be divided into one or more partial foil strips. In this instance, the foil roller control mechanisms of Preisner et al. control the foil advancement to substantially correspond with the presentation of the partial pressing surfaces so that foil roll contact is minimized and foil deposition is correlated only with the areas in which the partial pressing surfaces will be present.
Each of these systems involves the use of complex and correspondingly expensive custom pressing surfaces and/or motor controls to advance and halt the film. None of these systems solve the problem of managing selective foil deposition through computer-implemented control of a pressing roller assembly to achieve a more efficient foil deposition on selective areas of a printed substrate.